Stop whistleblower running into shower, say (7)
I believe the answer is:
refrain
'stop' is the definition.
(I've seen this before)
'whistleblower running into shower say' is the wordplay.
'whistleblower' becomes 'ref' (referee).
'running into' means one lot of letters goes inside another.
'shower' becomes 'rin' (I've seen this in another clue).
'say' becomes 'a' (I can't justify this - if you can you should give a lot more credence to this answer).
'rin' placed around 'a' is 'rain'.
'ref'+'rain'='REFRAIN'
Can you help me to learn more?
(Other definitions for refrain that I've seen before include "Chorus; desist" , "Stop activity" , "Main theme" , "tune" , "Kindly desist - from song?" .)